1. Field of the Invention
The present invention relates to a white light emitting diode (LED) which is formed by additionally applying green and red light emitting phosphors to a white LED in which a blue LED chip and a yellow light emitting phosphor are combined. In the white LED, the intensities of green and red light emission regions are increased, which have been relatively low. Therefore, it is possible to provide a white LED, of which the color representation is excellent and which can satisfy a hue angle value.
2. Description of the Related Art
In general, LEDs are referred to as semiconductor devices of which the light emitting sources are constructed by changing compound semiconductor materials such as GaAs, AlGaAs, GaN, InGaInP and the like, thereby implementing various colors of light.
Recently, as the semiconductor technology rapidly develops, high-luminance and high-quality LEDs as well as general-purpose low-luminance LEDs are being manufactured. Further, as high-characteristic blue and white LEDs are implemented, the application of LEDs is expanded into displays and next-generation lighting sources.
To apply such high-efficiency LEDs to various fields, a technique is frequently used, in which yellow light emitting phosphor is coated on a blue LED chip, thereby effectively inducing white light emission.
As for a method of implementing white light, a technique is widely applied, in which garnet-based yellow light emitting phosphor is coated on a blue LED chip. Recently, researches on a white LED, in which the blue LED chip and the yellow light emitting phosphor are combined, have rapidly developed. Upon the twenty-first century, various researches for implementing white LEDs with higher efficiency are being carried out in various fields such as LED chips, packages, and phosphors. In the field of phosphors among them, a silicate-based yellow light emitting phosphor is applied for an efficiency increase in white light emission, in addition to the existing garnet-based yellow light emitting phosphor.
FIG. 1 is a graph showing the light emission spectrum of a conventional white LED in which the blue LED chip and the silicate-based yellow light emitting phosphor are applied.
In the above-described silicate-based yellow light emitting phosphor, the full width at half maximum (FWHM) of a light-emission wavelength is narrow, because of a characteristic of europium 2+ doped with an activator. Therefore, as shown in FIG. 1, the intensities of a green light emission region G and a red light emission region R are relatively low, so that color representation is degraded and a hue angle value cannot be satisfied.